Electrically conducting polymers have been used in a variety of organic electronic devices, including in the development of electroluminescent (EL) devices for use in light emissive displays. With respect to EL devices, such as organic light emitting diodes (OLEDs) containing conducting polymers, such devices generally have the following configuration:                anode/hole injection layer/EL layer/cathode        
The anode is typically any material that has the ability to inject holes into the otherwise filled π-band of the semiconducting material used in the EL layer, such as, for example, indium/tin oxide (ITO). The anode is optionally supported on a glass or plastic substrate. The EL layer is typically semiconducting, conjugated organic material, including a conjugated semiconducting polymer such as poly(paraphenylenevinylene), polyfluorene, spiropolyfluorene or other EL polymer material, a small molecule fluorescent dye such as 8-hydroxquinoline aluminum (Alq3), a small molecule phosphorescent dye such as fac tris(2-phenylpyridine) iridium (III) (doped in a host matrix), a dendrimer, a conjugated polymer grafted with phosphorescent dye, a blend that contains the above-mentioned materials, and combinations. The EL layer can also be inorganic quantum dots or blends of semiconducting organic material with inorganic quantum dots. The cathode is typically any material (such as, e.g., Ca or Ba) that has the ability to inject electrons into the otherwise empty π*-band of the semiconducting organic material in the EL layer.
The hole injection layer (HIL) is typically a conducting polymer and facilitates the injection of holes from the anode into the semiconducting organic material in the EL layer. The hole injection layer can also be called a hole transport layer, hole injection/transport layer, or anode buffer layer, or may be characterized as part of a bilayer anode. Typical conducting polymers employed as hole injection layer include polyaniline and polydioxythiophenes such as poly(3,4-ethylenedioxythiophene) (PEDOT). These materials can be prepared by polymerizing aniline or dioxythiophene monomers in aqueous solution in the presence of a water soluble polymeric acid, such as poly(styrenesulfonic acid) (PSSA), as described in, for example, U.S. Pat. No. 5,300,575 entitled “Polythiophene dispersions, their production and their use”; hereby incorporated by reference in its entirety. A well known PEDOT/PSSA material is Baytron®-P, commercially available from H. C. Starck, GmbH (Leverkusen, Germany).
Electrically conducting polymers have also been used in photovoltaic devices, which convert radiation energy into electrical energy. Such devices generally have the following configuration: positive electrode/hole extraction layer/light harvesting layer(s)/negative electrode
The positive electrode and negative electrode can be selected from materials used for the anode and cathode of EL devices mentioned above. The hole extraction layer is typically a conducting polymer that facilitates the extraction of holes from the light harvesting layers for collection at the positive electrode. The light harvesting layer or layers typically consists of organic or inorganic semiconductors that can absorb light radiation and generate separated charges at an interface.
Aqueous electrically conductive polymer dispersions synthesized with water soluble polymeric sulfonic acids have undesirable low pH levels. The low pH can contribute to decreased stress life of an EL device containing such a hole injection layer, and contribute to corrosion within the device. Accordingly, there is a need in this art for compositions and hole injection layer prepared therefrom having improved properties.
Electrically conducting polymers also have utility as electrodes for electronic devices, such as thin film field effect transistors. In such transistors, an organic semiconducting film is present between source and drain electrodes. To be useful for the electrode application, the conducting polymers and the liquids for dispersing or dissolving the conducting polymers have to be compatible with the semiconducting polymers and the solvents for the semiconducting polymers to avoid re-dissolution of either conducting polymers or semiconducting polymers. The electrical conductivity of the electrodes fabricated from the conducting polymers should be greater than 10 S/cm (where S is a reciprocal ohm). However, the electrically conducting polythiophenes made with a polymeric acid typically provide conductivity in the range of about 10−3 S/cm or lower. In order to enhance conductivity, conductive additives may be added to the polymer. However, the presence of such additives can deleteriously affect the processability of the electrically conducting polythiophene. Accordingly, there is a need in this art for improved conducting polymers with good processability and increased conductivity.
U.S. Pat. No. 7,361,728 which is incorporated by reference in its entirety discloses the preparation of conductive polymer from a thiophene monomer with a mono-hyperbranched end-capping group. The hyperbranched groups were only located at the chain ends of each polymer and only imparted limited property enhancement to the conductive polymer. The monomer synthesis required complexed preparation and purification.
The synthesis of hyperbranched polymers has been recently disclosed. Hyperbranched polymers made by condensation reactions, have been suggested (Kim, et al., J. Am. Chem. Soc., 112, 4592 (1990); Hawker, et al. ibid, 113, 4583 (1991)), and synthesis of hyperbranched homopolymer via living chain polymerization process of vinyl monomers is disclosed by Frechet et al (Frechet, et al. Science, 269, 1080 (1995), U.S. Pat. Nos. 5,587,441, and 5,587,446, the disclosures of which are incorporated by reference herein in their entireties). Compared to dendrimer, hyperbranched polymers are less regular, but still may approximate at least some of the desirable properties of dendrimers (Frechet et al. J. Macromol. Sci., Pure Appl. Chem. A33, 1399 (1996), the disclosure of which is incorporated by reference in its entirety). More importantly, hyperbranched polymers are more conducive to industrial applications, especially those prepared via living chain polymerization processes.
Compared with linear and grafting polymers, dendritic polymers (or dendrimers) provide some unique advantages (Frechet, et al. Science, 269, 1080, 1995). First, the intrinsic viscosity of dendrimer is lower compared with linear analog with the same molecular weight. Second, the level of interaction between solvent and polymer is decreased and polymer becomes much more compact. Third, if the functional groups are located at the end of dendrimer, the functional group becomes more accessible and occupies much higher surface area. Since regularly branched dendrimers are typically prepared through lengthy multi-step syntheses, however, their availability is limited to a small group of functional monomers and industrial production of dendrimers is therefore limited.
Since the discovery of the synthesis of hyperbranched polymers by living chain polymerization process, various vinyl hyperbranched polymers have been prepared by living cationic polymerization (Frechet, U.S. Pat. No. 5,587,441), atom transfer radical polymerization (Wang, et al., WO 9630421 A1), group transfer polymerization, the disclosure of which is incorporated by reference in its entirety, and stable radical polymerization (Hawker, et al., J. Am. Chem. Soc. 113, 4583 (1991)). Vinyl hyperbranched polymers with different structures, such as random copolymer (Gaynor, et al, Macromolecules, 29, 1079 (1996), the disclosure of which is incorporated by reference in its entirety), grafted hyperbranched copolymer, and block hyperbranched copolymer, can be made by the above processes. The resultant vinyl hyperbranched polymers from living chain polymerization comprise a totally different class of materials from the above-mentioned dendrimer and its derivatives in terms of both chemical composition and macromolecular architecture.
Conducting polymer containing hyperbranched polymer and unique properties associated with hyperbranched polymers is not known.
Therefore what is needed is a process for fabrication of electrically conductive polymers and electrically conductive polymers produced having improved processibility, physical properties and optical properties.